"67 Showman what's the difference?

[RStar]

I been hearing a lot of talk about the Vibroverb. Can anyone tell me what the difference is between a Single Showman with 1 -15" speaker and a Vibroverb?
I own a '67 Showman head with a '69 Dual Showman cabinet with 2-15" EV SRO's. Ever hear of those?
I then had a replica '67 1-15" cabinet custom made and loaded a JBL D130F (never reconed) into it 3 years ago.
Both cabinet sound great. The D130 has more highs, but the EV SRO's break up smoother than the JBL. (The JBL breaks up a little flabby.)

Back to my question.....How would the Vibroverb compare to my Showman set ups? Still looking for the holy grail! Should I get a Vibroverb?

[Teleologist]

Have a '66 BF DS myself - small bottom with 2 D130f's.

First off there's a difference between the single & dual Showman heads - different output transformers(4 or 8 ohms) and the feedback circuit is different. Whichever you have, there's a mismatch with one of the cabs - not serious but it will affect the sound. If you're running a DS head with the 1x15 cab, you might try pulling 2 output tubes - either the outside pair(1 & 4) or the inside pair(2 & 3). This will reduce the power(~60 watts vs. 85), match the load, and should let it break up a little sooner. If you like the result, an easy mod if you want to switch back & forth and have a 3-prong cord, is to use what was the ground switch to lift the cathodes on 2 power tubes.

The Vibroverb is a very different amp. It's only 45 watts, has a tube rectifier, and the reverb circuit adds an extra gain stage. All 3 combine to let it break-up much more at lower volumes.

Nothin' wrong with a Showman though ;)

[RStar]

Teleologist,
Thanks for the advice. I've heard about pulling two of the tubes to reduce power, etc....but is there absolutely no chance of causing a problem? The 8 ohm transformer doesn't seem to be available and the rest of the head is stock. I'd hate to loose that original thing.
Also, if the Vibroverb was run at lower clean volumes would it then have a similar clean tone as the Showman? (Without reverb)

Does your '66 Dual actually have the word DUAL on the BF? I have a '66 catalog where the Dual Showman did NOT have the DUAL written on the BF. I read the only way to tell the difference for sure was to check out the transformer code number (4 vs. 8 ohms) and to check the value of the feedback resistor you speak of. Can you confirm this long unknown answer for me?

FYI,
With my Dual cabinet... I have disconnected one speaker to see if the load matching really made any difference. I couldn't tell much of a difference.

[Teleologist]

With a Fender tube amp, running a matched speaker load or up to 50% lower is better than running higher(can cause arcing in the OT and tube sockets). If you're worried about that 8 ohm OT, you're probably better off keeping things matched. If you did pull 2 tubes, the amp would want a 16 ohm load(both speakers in the DS bottom in series) and would be OK with 8. Pulling the tubes will make the remaining ones run hotter, so if they're biased really hot to begin with, it could send them over the edge. It will also raise the voltages somewhat so if any caps or resistors are borderline, it could send them over the edge.

IMHO, played clean BF Fenders all sound pretty similar - the ratio of highs to mids to bass is roughly the same(common tone stacks, circuits, etc.). Although they have SS rectifiers, the big trannies in the Showmans and Twins make for a nice big sound provided the volume can be dialed up to at least 4. Good power tubes and slightly warmer bias settings help too. I have four Phillips/Sylvania 7581As(an industrial version of the Sylvania STR) in mine biased at 42-43ma. each. I occasionally run 5881s in my BF DR and with the D120f in it, it sounds like a mini-Twin or the Showman on clean settings.

Mine doesn't have the word Dual on it. A band I was in bought 3 of them in '66 - two Duals and a 1x15 Single with a D140f in it for bass. If I'm remembering right there was no easy way to tell the heads apart until we stenciled 'em.